fix: respect explicitly empty Stryker mutation scope

[canblmz1]

When a project sets Stryker mutate: [], Tautest currently treats it as an absent setting and starts mutation-testing changed source files. Preserve the empty list so the CLI returns a no-op (exit 2) before creating reports or starting Stryker.

Adds core/CLI regression tests, documents the behavior, and extends the packed compatibility canary to cover the disabled scope. The fixture now declares its root package for pnpm 10; workflow-source tests normalize CRLF like the other workflow tests.

Validation:

• Typecheck, lint, build and production dependency audit passed.
• All package/example tests passed (core 226, CLI 49, GitHub Action 50, and example suites).
• Packed CLI/core passed on Node 22 with Stryker 10.0.0 + Vitest 4.1.11 (7 killed / 4 survived); the Vitest 5.0.2 combination correctly refused zero-test scoring. Both installations returned exit 2 for mutate: [].
• Full pnpm test has two existing Windows-specific Changesets harness failures: executable-bit handling and a directory symlink requiring privileges. These are outside the scope fix; Linux CI still needs to run. No npm publication attempted.
• GitHub CI subsequently passed all 13 checks on this commit: Node 22/24 release readiness, npm/Yarn packed installations, Action mutation smoke, and all eight packed Stryker/Vitest combinations. The local Windows harness limitations above remain recorded; the complete Linux test runs are green.

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